In semiconductor processes, foreign substances (also referred to as defects in the broad sense of the term) on the surface of a semiconductor substrate (wafer) cause insulation failures and short circuits between wirings, and also cause insulation failures of capacitors and breakages of oxide films, and the like. The foreign substances includes substances such as created from moving parts of a carrier, device, created from human bodies, created in chemical reactions in processing devices in which process gases are used, and mixed in medicals and materials. Then these foreign substances are attached to the surface of the wafer for various reasons. In addition, in the manufacturing process of a liquid crystal display element, if a foreign substance gets mixed in a pattern of the display element, this liquid crystal display element can not be used as a display element. Further, the same can be said for the case of the manufacturing process of a printed-circuit board, and the contamination with foreign substances leads to short circuits and contact failures between patterns. Therefore, in order to manage the process yield, it becomes important to detect foreign substances on substrates such as a wafer and feed back the information to the manufacturing process.
Apparatuses that are used for detecting foreign substances and the like on the above-mentioned substrates are so-called inspection apparatuses. The inspection apparatuses can be roughly classified into two types: one type is a surface inspection apparatus for inspecting mirror surface wafers, and the other type is a wafer-with-patterns inspection apparatus for inspecting wafers on which circuit patters are formed. In particular, Patent Literature 1, Patent Literature 2, and Patent Literature 3 are well known as wafer-with-patterns inspection apparatus for inspecting wafers on which circuit patters are formed. In Patent Literatures 1 to 3, an illuminated region having a two-dimensional spread in the major axis direction and the minor axis direction is formed on a substrate. Patent Literature 4 and Patent Literature 4 are well known for disclosing the related art regarding another inspection apparatus. In addition, Patent Literature 6 is well known for disclosing a technology for illuminating a substrate. Patent Literature 7 and Patent Literature 8 are well known for disclosing other technologies.